1. Field of the Invention
The present invention relates to an electrostatic chuck which is useful, for example, in fixing, flatness correction and transporting a semiconductor wafer in an apparatus adapted for fabricating a semiconductor wafer, such as an etching apparatus, an ion implanter, or an electron beam exposing apparatus.
2. Description of the Related Art
In a semiconductor production apparatus or the like, conventionally, an electrostatic chuck is used in conjunction with a process such as dry etching, warpage correction, or transporting a semiconductor wafer while fixing the wafer to the chuck via a vacuum.
In a known electrostatic chuck of this kind, a disk-like ceramic body having an embedded suction electrode and a disk-like aluminum base are joined and integrated with one another. Also, an electrostatic chuck in which a heating element is embedded in a ceramic body for the purpose of heating a semiconductor wafer is known (see JP-A-2004-71647 (page 4, FIG. 1)).
An electrostatic chuck having such a heating element must have a uniform surface temperature distribution which heats a semiconductor wafer in order to enhance processing accuracy. Namely, when there is a temperature variation within a semiconductor wafer, processing accuracy, for example, of etching is lowered, and hence the entire face of the semiconductor wafer desirably is uniformly heated by the heating element.
3. Problems to be Solved by the Invention:
In the above-mentioned aluminum base, as shown in FIGS. 10A and 10B, a through hole P3 which passes in the thickness direction is formed, for example, to dispose terminals for supplying current to the suction electrode P1 and the heating element P2. The aluminum base P4 is not in direct contact with the ceramic body P5 in the portion of the through hole P3, which can result in non-uniform heating.
For example, a method in which, in order to instantaneously change the temperature of the ceramic body P5 during an etching process, the ceramic body P5 generates heat and at the same time the aluminum base P4 is cooled will be considered. In this method, the temperature of the ceramic body P5 is locally raised by heating element P2, in the portion of the through hole P3 where the aluminum base P4 is not in direct contact with the ceramic body P5. Consequently, a problem arises in that the temperature distribution in the ceramic body P5 deteriorates (i.e., is made non-uniform).